System for space-scanning with a radiated beam of wave signals



A. v.' Louer-@REN 2,409,944 SCANNING WITH A RADIATED BEAM O WAVE SIGNALSSYSTEM FOR SPACE- 'origina1. Fi1ed May 2e, 1941 INVENTOR ART RV.LOUGHREN ATTORNEY Patented Oct. 22, 1946 UNITED STATES PATENT FFICEOriginal application May 26, 1941, Serial No.

395,172. Divided and this application Novem'- ber 12, 1941, Serial No.418,712

1c claims. (ol. 25o-11') This invention relates to systems forspacescanning with a radiated beam of wave signals and, while theinvention is of general application, it is oi particular utility insystems of the type in which a predetermined space is scanned with asharply-concentrated radiated beam in order to locate a radiated-signalreector, such as an aircraft.

The present application is a division of applicants copendingapplication Serial No. 395,172, filed May 26, 1941, for a System forlocating a radiated-signal reector.

It has been proposed inr aircraft locating systems to scan apredetermined space in two directions with a sharply-concentratedradiated beam of wave signals and to receive the signal which is reectedfrom the aircraft to provide an indication of its direction from thelocating station. It has also been proposed to deflect the radiated beamat adiierent frequency in each of two directions in order to scan agiven space and to utilize a cathode-ray tube at the receiving stationas the direction-indicating device, the electron beam of the cathode-raytube being deected synchronously with the deection of the radiated beam.However, such systems of the prior art have had the disadvantage thatmechanical beam-dellectng arrangements were necessary for causing theradiated beam to scan the desired space. The general disadvantages ofmechanical scanning arrangements are well understood by those skilled inthe television art and many of these disadvantages arev also present inmechanical scanning arrangements of the type under consideration.

It is an object of the present invention, therefore, to provide animproved system for scanning a p-redetermined space with asharply-concentratedl radiated beam of wave signalsY which is notsubject to one or more of the disadvantages of-prior art systems of thetype mentioned above. I Itis ya further object of the invention toprovide a nonmechanical scanning system for scanning predetermined spacewith a radiated beam ofwave signals. Y

. In accordance with a feature Yof the invention, a system for scanninga predetermined space with a radiated beam comprises, a radiating systemincluding a plurality of signal radiatorslgeometrically spaced in eitherof two dimensions, `or both, means including a plurality of electricaldelay networks for electrically spacing the signal radiators in one ofthe dimensions, and a source of high-frequency Wave signals. This*signal comprises means'for individually applying wave sigsol 2 nals fromsaid source to the signal radiators for directive radiation effectivelyin the form of a sharply-concentrated beam and means for varying thefrequency of the wave signals effectively to vary the relative phase ofthe signals as applied to the signal radiators which are spaced in oneof the two above-mentioned dimensions thereby to vary the direction oftransmission of the radiated beam to eiect a scanning operation in onedimension. If the radiators are geometrically spaced in two dimensions,the system includes also means for varying the relative phase' of thesignals as applied to said signal radiators which' are spaced in theother of said predetermined dimensions at a second predeterminedfrequency, thereby to vary the direction of transmission of the radiatedbeam in two dimensions to' scan a predetermined space.

For a better understanding of the invention, together withother andfurther objects thereor, reference is had to the following descriptiontaken in connection with the accompanying drawing and its'scope will bepointed out inthe appended claims.

Fig. 1 of the drawing is a circuit diagram, partly schematic, of asystem for scanning a predetermined space with a sharply-concentratedradiated beam of wave signals; and Fig. 1a comprises a set of'graphswhich are used in explaining a portion of the operation of thearrangement of Fig. 1'.

. Referring now more particularly to Fig. 1 of the drawing, the systemthere represented comprises an antenna system IU, means for applying awave signal tothe antenna system for directive radiation eiectively inthe form of a sharplyconcentrated bieam,. and means for cyclicallyVarying the frequency of the wave signal and, by virtue of the antennacharacteristics as described hereinafter, causing the beam to scan apredetermine'drspace in one direction. lI'he antenna system l0 includesa plurality of directional signal radiators vshown as dipoles D1-D24,inclusive, geometrically, or vphysically spaced in two dimensions andelectrically spaced` in` one dimension. Specifically, the conductors ofthe dipoles are all disposed in the same horizontal plane and areparallel to'each other,v Dipoles Di-Ds, inclusive, are spaced in a' rstdimension in a longitudinal array, while the sets of dipoles 13a-D12,inclusive, D13-Dra, inclusive, and Die-D24, inclusive, are similarly Yspaced in other horizontal arrays and are arranged, in the order named,tov one side of the set of f ipolesK D15-D6, inclusive, to form an arrayof dipole sets, each set including an array of six dipole antennae andthe sets being spaced in a second dimension. The dipoles of each of theabove-mentioned sets of dipoles are energized in parallel except thatthe above-mentioned electrical spacing in the one dimension between theindividual dipoles of the sets is provided by delay networks Finterposed between adjacent dipoles.

The geometrical spacing of the dipoles in each lset in theabove-mentioned one dimension is preferably made approximately one-halfwave length of the mean or nominal frequency of the wave signal to beapplied to the system, while the electrical spacing due to delaynetworks F, F is made to be an integral number of wave lengths at'thenominal or mean frequency of the system. The sets of dipoles are alsopreferably spaced in the dimension normal to the sets, or in theabovementioned second dimension, by a distance approximately equal toone-half the wave length of the mean or nominal frequency of the Wavesignal t be applied to the system. j

The means for applying a Wave signal to the antenna system I9 fordirective radiation effectively in the form of a sharply-concentratedbeam comprises a high-frequency oscillator II of any suitable typeadapted for frequency modulation individually coupled to each of thesets of dipoles through transformers Ta, Tb, Te, and Td having theirprimary windings connected in series and coupled to the high-frequencyoscillator II and their respective secondary windings coupled to theabove-mentioned sets of dipoles through phase Shifters I2a, I2b, I2C,and I2cl, respectively, which have the same phase shift at the nominalor mean value of the field-frequency generator.

In order to vary the relative phase of the signals as applied to thesignal radiators of antenna system I0 which are spaced in theabove-mentioned one dimension at a first predetermined frequency, thereis provided means for varying the frequency of the signal developedbythe high-frequency oscillator II at the above-mentioned firstpredetermined frequency. Specifically, there is provided aline-frequency generator I3 which is adapted to be synchronized from altimer I4, the output circuit of the line-frequency generator I3 being`coupled to high-frequency generator II in order to vary the outputfrequency ofithis unit in accordancewithV the wave form of the signaldeveloped by line-frequency generator I3, in any conventional manner.

In order to vary the relative phase of the signals as applied to thesignal radiators of antenna I0 which are spaced in the above-mentionedsecond dimension at a second predetermined frequency, there is provideda field-frequency gen'- erator I5, also adapted to be synchronized bytimer I4 and having an output circuit coupled across a voltage-dividerresistor 9, the mid-tap of which is grounded. A control voltage isderived from one end of resistor 9 and utilized to control phase shifterI2a while a Voltage of opposite polarity is derived from the other endof resistor 9 and utilized to control phase shifter I2d. Controlvoltages for phase Shifters l2band I2C are derived from intermediatepoints on resistor 9 as illustrated in the drawing. The phase ShiftersI2a -i2d, inclusive, may be of any conventional type and it is to beunderstood that the phase shift of each of these units is dependent uponthe magnitude and polarity of the control voltage derived from theresistor 9 for the particular unit under consideration.

In order to suppress radiation downward from the plane including theconductors of dipoles Di-Dzi, inclusive, a reflecting conductor I'I isdisposed below each of the dipoles. These reflectors increase the usefulenergy in the desired direction of radiation and minimize minor spuriousbeams.

'In considering the operation of the system of Fig. 1 and neglecting forthe moment the functions of generators I3 and I5, it will be seen thatthe system comprises a plurality of directional signal radiatorsgeometrically spaced in the above-mentioned first dimension and in theabove-mentioned second dimension and that the signal radiators which aregeometrically spaced in the first dimension are also electrically spacedby a time-phase displacement due to time-delay units F. Considering forthe moment only the set of dipoles Di-Da, inclusive, in the conditionwhere they are all excited in the same phase, it is seen that this is aknown form of antenna array by which the radiation is concentratedrelative to the radiation pattern of a single dipole. The concentrationof energy into the beam takes place at the expense of the regionsgenerally in the direction of the ends of the row of dipoles.Furthermore, it is seen that the reflectors I'I limit or suppress asubstantial part of the radiation in the direction in which they arespaced from their associated dipole conductors. The resulting radiationpattern has a fan-shaped configuration with its major dimensionvertically above the'row of dipoles, its smallest dimension parallel tothe row, and its intermediate dimension parallel to the individualdipoles.

. The effect of adding the other sets of dipoles is to concentrate theradiated signal to the form of a sharply-concentrated beam. In the casewhere all rows are excited with a common phase the direction of thisbeam will be at right angles to the plane of the lcomplete array. Thereason for this is that the signals radiated from any pair of antennaeare in phase only in the direction normal to the plane containing thedipoles.

Considering now the function of `line-frequency generator I3, it is seenthat it is effective to vary the frequency of the output of oscillator II cyclically and directly in accordance with its wave form, which ispreferably a linear saw-tooth wave form.I Due to the fact that thedipoles of each of the above-mentioned sets are electrically spaced bythe time-delay networks F, the effect of this frequency variation is tovary the relative phase of the excitation of the dipoles of each set.VThus, for a frequency somewhat different than the nominal or meanfrequency of the system, the signals radiated by each of a pair ofadjacent dipoles of a set are not in phase in the vertical direction butare in phase in a direction displaced therefrom by an amount dependentupon the relative phase of antenna excitation. Thus, the line-frequencygenerator I3 comprises means for Varying the phase of thesignal asapplied to the signal radiators of each of the abovementioned sets atthe frequency of the signal generated by line-'frequency generator I3 asa result of the frequency variation of the output of oscillator II byline-frequency generator I3 and for eecting space-scanning by theconcentrated radiated beam in lines in the above-mentioned onedimension. Y If the effect of field-frequency generator I5 is nowconsidered, it is seen that the voltage output of this generator, whichis also preferably E, of a linear saw-tooth wave form, is effective tovary the relative phase of the dipoles which are spaced in theabove-mentioned second dimension at the frequency of this generator.Reference is made to Fig. la for an explanation of the operation of thisgenerator. Thus, curves lla, 1lb, llc, and il'd represent the controlvoltages applied to phase Shifters 62a, l2b, I2C, and IZd, respectively.It is thus seen that, at the beginning of the field-trace period, thesignals applied to sets of dipoles Di-DG, inclusive, and Bft-D12,inclusive, are shifted in phase in one sense and by different amountsand that the signals applied to sets of dipoles D13-D18, inclusive, andDis-D24, inclusive, are correspondingly shifted in phase in the oppositesense and by different amounts. The result of this excitation is to tiltthe transmitted beam in the above-mentioned second dimension because itis only in such a direction that the signals radiated by two adjacentdipoles which are spaced in the second dimension, for example, dipolesDe and D12, are exactly in phase. Furthermore, it is seen that theamount of this tilt in the seco-nd dimension changes during thefield-scanning period due to the change of relative excitation phase ofthe sets of dipoles eected by field-scanning generator I5. Specifically,the amount of tilt in the second dimension decreases to Zero, at whichtime the beam is vertical and then increases in the opposite sense. Thearrangement of Fig. l is thus effective to vary the direction oftransmission of the sharply-concentrated beam in two directions to scana predetermined space with the beam.

While applicant does not intend to limit the invention to any particulardesign constantsthe following values are appropriate for a system forscanning space with a radiated beam for use in a plane-locating system:

Mean or normal frequency for oscillator l1 10D-1000 megacycles Frequencyof line-scanning generator 13 50G-5000 cycles Frequency offield-scanning gen` erator 15 10-30 cycles 5 to 10 periods at nominalcarrier frequency.

It has heretofore been stated that the spacing between the dipoles ofthe sets of dipoles Di-De, inclusive, Bfr-D12, inclusive, etc., ispreferably made approximately one-half wave length of the mean ornominal frequency of the operating frequency range of the antennasystem. When the networks F have a time delay of iive periods at thenominal operating frequency of the system, it will be evident that thenetworks provide between any adjacent pair of dipoles an electricalspacing having a value, measured in wave lengths of the nominaloperating frequency of the sys- Time delay of Networks F Vtem, ten timesthe value of physical spacing of the dipoles of a set. Likewise, a timedelay of ten periods provides an electrical spacing twenty times thephysical spacing. Electrical spacings of ten to twenty times thephysical spacings, as referred to adjacent pairs of dipoles, are of ahigher order of magnitude than thephysical spacings and this is themeaning of the term higher order of magnitude as used in the appendedclaims.

While there has been described what is at present considered to be thepreferred embodiment of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed in the appended claims to cover all such changes and modificationsas fall Within the true spirit and scope of the invention.

What is claimed is: 1. A system for scanning a predetermined space witha radiated beam comprising, a radiating system including a plurality ofsignal radiators geometrica'lly spaced in one dimension, means includinga plurality of electrical delay networks for electrically spacing saidsignal radiators in said one dimension, a source of high-frequency wavesignals, means for individually applying Wave signals from said sourceto said signal radiators for directive radiation effectively in the formof a sharply-concentrated beam, and means for varying the frequency ofsaid wave signals effectively to vary the relative phase of said signalsas applied to said signal radiators, thereby to vary the direction oftransmission of said radiated beam.

2. A system for scanning a predetermined space with a radiated beamcomprising, a radiating system including a plurality of signal radiatorsgeometrically spaced in one dimension and means for electrically spacingthem in the said one dimension, a source of high-frequency wave signals,means for individually applying wave signals from said source to saidsignal radiators for directive radiation effectively in the form of asharply-concentrated beam, and means comprising said electrical spacingmeans and means for varying the frequency of said wave signalseffectively to vary the relative phase of the signals as applied to saidradiators which are spaced in said one dimension at a firstpredetermined frequency, thereby to vary the direction of transmissionof said radiated beam to eect a scanning operation in said onedimension.

3. A system for scanning a predetermined space with a radiated beamcomprising, a radiating system including a plurality of signal radiatorsgeometrically spaced in two dimensions and means for electricallyspacing them in one of the two dimensions, a source of high-frequencyWave signals, means for individually applying wave signals from saidsource to said signalr radiators for directive radiation effectively inthe form of a sharply-concentrated beam, means comprising saidelectrical spacing means and means for varying the frequency of saidwave signals eiectively to vary the relative phase of the signals asapplied to said radiators which are spaced in said one dimension at alirst predetermined frequency, and means for varying the relative phaseof said signals as applied to said signal radiators which are spaced inthe other dimension at a second predetermined frequency, thereby to varythe direction of transmission of said radiated beam in two dimensions toscan a predetermined space.

4. A system for scanning a predetermined space with a radiated beamcomprising, a radiating system including a plurality of signal radiatorseffectively grouped in one dimension in a plurality of arrays which arespaced in alignment in another dimension, means for electrically spacingsaid signal radiators in said one dimension, a source of high-frequencywave signals, means for individually applying wave signals from saidsource to said signal radiators for directive radiation eifectively inthe form of' a sharply-concentrated beam, means comprising saidelectrical spacing means and means for varying the frequency of saidwave signals effectively to vary the effective phase of the signals asapplied to said radiators which are spaced in said one dimension at afirst predetermined frequency, and-means for varying the relative phaseof said signals as applied to said signal radiators which are spaced insaid other dimension at a second predetermined frequency, thereby tovary the direction of transmission of said radiated beam in twodimensions to scan a predetermined space.

5. A system for scanning a predetermined space with a radiated beamcomprising, a radiating system including a plurality of signal radiatorsgeometrically spaced in two dimensions and means for electricallyspacing them in one of the two dimensions, a source of high-frequencywave signals, means for individually applying wave signals from saidsource to said signal radiators for directive radiation eiectively inthe form of a sharply-concentrated beam, means comprising saidelectrical spacing means and means for varying the frequency of saidwave signals in accordance with a saw-tooth wave form effectively tovary the relative phase of the signals as applied to said radiatorswhich are spaced in said one dimension at a first predeterminedfrequency, and means for varying the relative phase of said signals asapplied to said signal radiators which are spaced in the other dimensionat a second predetermined frequency, thereby to vary the direction oftransmission of said radiated beam in two dimensions to scan apredetermined space.

6. A radiated-signal translating system having a sharply-directivecharacteristic variable in one direction with frequency over apredetermined operating frequency range and variable in anotherdirection with phase comprising, a plurality of radiated-signaltranslators physically spaced in two dimensions by predetermined wavelength values at the nominal frequency of said range, a wave-signaltranslating circuit, means coupling said translators to said circuit andproviding between any adjacent pair of translators spaced in one of thetwo dimensions an electrical spacing having a wave length value at saidnominal frequency of a higher order of magnitude than said predeterminedvalue of physical spacing of said pair of translators, whereby saidsystem has a sharply directive characteristic having a maximum value ina direction which varies with the frequency of a wave signal translatedby said radiated-signal translators, and translating means interposedbetween said translators which are spaced in the other dimension andsaid wave-signal translating circuit for effectively varying therelative phases of the wave signals translated between said translatorsspaced in said other dimension and said circuit, whereby the directivecharacteristic of said system has a maximum value in a directionadditionally varying with the relative phases of said last-mentionedtranslated wave signals.

7. An antenna system having a sharply-directive characteristic variablein one direction with frequency over a predetermined operating frequencyrange and variablein another direction with p-hase comprising, aplurality of antenna elements physically spaced in two dimensions bypredetermined wave length values at the nominal frequency of said range,a wave-signal vtranslating circuit, means coupling said elements to saidcircuit and providing between any adjacent pair of elements in one ofthe two dimensions an electrical spacing having a wave length value atsaid nominal frequency of a higher order of magnitude than saidpredetermined value of physical spacing of said pair of elements,whereby said system has a sharply-directive characteristic having amaximum value in a direction which varies with the frequency of a wavesignal translated by said antenna elements, and translating meansinterposed Ibetween said antenna elements which are spaced in the otherdimension and said wave-signal translating circuit for effectivelyvarying the relative phases of the wave signals translated between saidantenna elements spaced in said other dimension and said circuit,whereby the directive characteristic of said system has a maximum valuein a direction additionally varying with the relative phases of saidlast-mentioned translated wave signals.

8. A radiated-signal translating system having a sharply-directivecharacteristic variable in direction with frequency over a predeterminedoperating frequency range comprising, a plurality of radiated-signaltranslators physically spaced in one dimension by predetermined wavelength values at the nominal frequency of said range, a wave-signaltranslating circuit, and wave-signal delay means coupling saidtranslators to said circuit and providing between any adjacent pair oftranslators an electrical spacing having a wave length value at saidnominal frequency of a higher order of magnitude than said predeterminedvalue of physical spacing of said pair of translators, whereby saidsystem has a sharply-directive characteristic having a maximum value ina direction which varies with the frequency of a Wave signal translatedby said radiated-signal translators.

9. A radiated-signal translating system having a sharply-directivecharacteristic variable in direction with frequency over a predeterminedoperating frequency range comprising, a plurality of radiated-signaltranslators physically spaced in one dimension by predetermined wavelength values at the nominal frequency of said range, a wave-signaltranslating circuit, and a plurality of electrical delay networksindividually interposed between said translators for coupling saidtranslators to said circuit and for providing between any adjacent pairof translators an electrical spacing having a wave length value at saidnominal frequency of a higher order of magnitude than said predeterminedvalue of physical spacing of said pair of translators, whereby saidsystem has a sharply-directive characteristic having a maximum value ina direction which varies with the frequency of a wave signal translatedby said radiated-signal translators.

10. An antenna system having a sharply-directive characteristic variablein direction with frequency over a predetermined operating frequencyrange comprising, a plurality of antenna elements physically spaced inone dimension by prede-v termined wave length values at the nominalfrequency of said range, a wave-signal translating circuit, andwave-signal delay means coupling said antenna elements to said circuitand providing between any adjacent pair of elements anelectrical-spacing having a wave length value at said nominal frequencyof a higher order of magnitude than said predetermined value of physicalspacing of said pair of elements, whereby said system has asharply-directive characteristic having a maximum value in a directionwhich varies with the frequency of a wave signal translated by saidantenna elements.

ARTHUR V. LOUGHREN.

